Nowadays, the technological improvements in cameras, lenses, films or reproduction material have been perfected to such an extent that taking pictures, movies or video is now reduced to its fundamentals, that is, aesthetic factors remain to be chosen: the subject, its composition, optical treatment, and the light. The first three factors are under full control of the user; however, the latter, the light, is not. Yet, light in a picture, scenography and evidently, photographs, movies or video is probably the determinant component governing in a subtle, albeit deep, way the aesthetic quality of the reproduction.
In substantial opposition to the degree of control over these fundamentals given to the user by the present technology, light is measured by light meters which operate based on a very primitive concept that has not evloved since its discovery. A light meter measures only the luminous power that reaches it. But nearly none of the subjects photographed have a luminous power of their own. In fact, they just reflect light. Therefore, this power depends basically on (a) the luminous power that reaches the subject, and (b) the reflecting characteristics of each particular subject, which vary according to its color, value (whereby "value" is considered as a grade of gray in a scale going from black to white) and superficial texture. The final result of the interaction of both variables is what finally reaches the light meter.
As an extreme example, we can obtain the same luminous power measuring two completely different subjects: a brightly lit navy blue subject and a dimly lit pale yellow subject. Present light meters are unable to tell the difference. But of course the user can do it.
All light meters, since the first simple ones to the sophisticated new models, handle this situation in the most primitive fashion. They assume that the subject--the light of which is being measured--always shows a color and/or value equal to a standard grade of gray which is universally accepted. Based on this assumption, they recommend in manual or automatic mode the shutter speed and diaphragm aperture settings needed to take a photograph, that is to say, those needed to reproduce that subject, whose luminosity value are unknown and have therefore been simply assumed as being equal to a standard grade of gray in the film as standard grade of gray. This fact is not well-known and the results may surprise.
Since the noted problem is so obvious in high contrast situations, very dark or very light subjects against very light or very dark backgrounds, different mechanisms have been incorporated in some cameras or light meters in order to perform primitive and empirical adjustments, with the advancements reached in micro electronics and computers, the problem is being dealt with in a way that seems very sophisticated but in fact continues being primitive: they compensate there high contrast situations by means of dividing the subject in partial areas, partial measurement of the light and their subsequent integration. But the problem that the light meter does not perceive the color and/or value of the subject remains untouched.
On the other hand, of the different reproduction means: film, orthicons or vidicons, etc., have a sensibility specturm to light which is completely different from the human eye-brain system. For instance, if the same subject is observed and photographed at constant shutter speed and diaphragm--aperture settings and lighted with an external source having L power, and in subsequent photographs the light is reduced to L/4 or L/32 and is then increased to 4L or 32L, the film will register the light reduction or increase with a higher magnitude than the human eye. All this leads to a fact that seems to have been forgotten: only the user knows what his subject is and how he wants it to be reproduced. And he knows this directly without any instrument. Therefore, the problem is to find the manner to provide the light meter with this information, generated by the most efficient of the processing systems: the human brain, instead of trying to obtain a minor and rather irrelevant part of this information, using costly and complex microelectronic gadgetry. Oddly, the latter seems to be the most popular alternative, but it will not lead too far.
The object of the present invention is to follow another, more practical, rational and suitable way. Basically, it consists of giving up the simplistic assumption of the standard gray and informing the light meter what colors and luminous values it is measuring and, above all, how they should be reproduced, and informing the light meter of the light sensitivity behavior of the film being used.